Simulation and analysis of coalescence of water droplets on composite insulating surface under DC electric field

This paper is aimed at numerical simulations and experiments on the coalescence of pairs of sessile water droplets deposited on dielectric composite insulating surfaces. The mechanisms as well as parameters involved in coalescence under the influence of DC electric field are investigated. A mathematical approach based on a diffuse interface model that essentially consists of a coupling between Navier-Stokes equations, the computing of electric force and a Cahn-Hilliard type equation describing the interface evolution including capillary phenomena, is developed. Experiments are performed to analyze the behavior of these water droplets depending on their size, conductivity and location with respect to electrodes as well as the hydrophobicity of insulator. Simulations showed reasonably good agreement with the experimental data. It also showed that the coalescence process depends mainly on three parameters: the location of the droplets on the insulating surface, the volume of the droplets and the distance between droplets.